title: Role of tyrosine residue in methane activation at the dicopper site of particulate methane monooxygenase: a density functional theory study.
abstract: Methane hydroxylation at the dinuclear copper site of particulate methane monooxygenase (pMMO) is studied by using density functional theory calculations. The electronic, structural, and reactivity properties of a possible dinuclear copper species (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) are discussed with respect to the C-H bond activation of methane. We propose that the tyrosine residue in the second coordination sphere of the dicopper site donates an H atom to the μ-η(2):η(2)-peroxoCu(II)Cu(II) species and the resultant (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) species can hydroxylate methane. This species for methane hydroxylation is more favorable in reactivity than the bis(μ-oxo)Cu(III)Cu(III) species. The H-atom transfer or proton-coupled electron transfer from the tyrosine residue can reasonably induce the O-O bond dissociation of the μ-η(2):η(2)-peroxoCu(II)Cu(II) species to form the reactive (μ-oxo)(μ-hydroxo)Cu(II)Cu(III) species, which is expected to be an active species for the conversion of methane to methanol at the dicopper site of pMMO. The rate-determining step for the methane hydroxylation is the C-H cleavage, which is in good agreement with experimental KIE values reported so far.
authors.affiliation: Institute for Materials Chemistry and Engineering and International Research Center for Molecular System, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shiota
authors.forename: Gergely
authors.initials: G
authors.lastname: Juhász
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshizawa
mesh_terms: D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D042083:Methylocystaceae / Q000737:chemistry / Q000201:enzymology*; D020581:Methylosinus / Q000737:chemistry / Q000201:enzymology*; D008958:Models, Molecular; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003300:Copper; D010105:Oxygenases; C021555:methane monooxygenase; D008697:Methane